First of all, he’s still a Democrat, if an unpopular one. They aren’t going to excommunicate him.
Second, politicians are politicians, and some Virginia Democrats will collaborate with him to achieve mutual goals. Even if they aren’t as high-profile as usual.
Want to know what will happen to Northam? Just look at what happened to Mayor Rahm Emanuel. He is passionately hated throughout Chicago, and he didn’t even wear blackface (to my knowledge). Still very powerful, because other politicians need him to get shit done.